Two retired RUC officers are involved in the re-investigation into a murder by a loyalist unit allegedly headed by a police agent, the High Court heard today.

Confirmation came as the victim's mother challenged a PSNI policy of rehiring policemen and women who left under sweeping reforms.

Lawyers for Vivienne McCord claimed officers who received generous severance packages were returning by "the back door".

Her challenge to multi-million pound civilian contracts is being heard alongside a legal bid by public sector union NIPSA to stop police hiring up to 1,000 temporary staff.

It was claimed in both cases that the arrangements are unlawful because they involve investigatory duties.

Mrs McCord's 22-year-old son, Raymond McCord Jr, was beaten to death before his body was dumped in a quarry near north Belfast in 1997.

No one has ever been convicted of the former RAF man's murder.

His killing was at the centre of a damning report by former Police Ombudsman Nuala O'Loan which established evidence that rogue Special Branch officers colluded with a north Belfast UVF gang responsible for up to 16 deaths.

Mrs McCord fears that bringing ex-policemen back in to help with historical inquiries may thwart efforts to establish the full circumstances surrounding her son's murder.

Her legal team is seeking to judicially review the Chief Constable's policy of contracting former officers who left with redundancy packages under the Patten reforms.

In court today details of the re-investigation into the McCord killing were set out.

A statement from a senior PSNI commander confirmed that two former RUC officers brought in as civilian staff on a temporary basis were involved as assistants.

It was stressed that neither were members of Special Branch or worked on the original investigation.

They have also signed declarations that they have no connections to any suspects.

But Frank O'Donoghue QC, for Mrs McCord, contended: "This is very clear evidence of those contract workers working in an investigatory role."

The case centres on contracts with Grafton Recruitment and Resource NI to provide civilian workers and support services.

Mr Justice Treacy was told that the Police (NI) Act 2000 only allowed such staff to carry out detention and escort duties.

It was argued that former RUC officers are remaining at the heart of investigating past criminality, including suspected police wrongdoing.

According to Mr O'Donoghue the Chief Constable has acted outside the law.

Contracting out any investigatory work in historic murder cases would inevitably attract former RUC officers, the barrister claimed.

He also pointed out how RUC officers who retired under the Patten arrangements would lose their pension if they were directly re-employed by PSNI within five years.

"Those police officers were being paid off with generous packages because they were no longer being able to perform their policing skills," Mr O'Donoghue added.

"In fact they are being brought back effectively through the back door, with their pension and being able to perform the functions.

"This court could never determine that the legislature intended that all of those services could be outsourced in this way."